Liquid ejecting head and liquid ejecting apparatus

ABSTRACT

At an area corresponding to a pressure chamber, the width of a lower electrode film in a nozzle row direction is narrower than the width of the pressure chamber in the same direction. A vibrating plate at the area corresponding to a pressure chamber includes an area P 1 , an area P 2 , and an area P 3 . The area P 1  is an area on which the piezoelectric layer to be an activation portion is stacked. The area P 2  is an area on which the piezoelectric layer to be an inactivation portion is stacked. The area P 3  is an area on which the piezoelectric layer is not stacked. When the thicknesses of the vibrating plate at the areas P 1 , P 2  and P 3  are set to, respectively, t 1 , t 2 , and t 3 , the following expression is satisfied:
 
 t 1&gt; t 2≧ t 3  (1).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 14/603,939 filed on Jan. 23, 2015, now U.S. Pat. No. 9,132,637,which claims priority to Japanese Patent Application No. 2014-024066filed on Feb. 12, 2014, which applications are hereby incorporated byreference in their entirety.

BACKGROUND

1. Technical Field

Embodiments of the present invention relate to a liquid ejecting headthat ejects liquid by driving a piezoelectric element and to a liquidejecting apparatus that includes the liquid ejecting head.

2. Related Art

A liquid ejecting apparatus is an apparatus that includes a liquidejecting head. For example, an ink jet printer and an ink jet plotterare examples of the liquid ejecting apparatus. Various types of liquidcan be ejected from the liquid ejecting head.

Recently, the liquid ejecting apparatus has been also applied to orincluded in various manufacturing apparatuses because of the liquidejecting apparatus has the advantage of being able to accurately impactor deposit very small amounts of liquid at a predetermined position. Theliquid ejecting apparatus has been applied to or included in, forexample, a display manufacturing apparatus, an electrode formingapparatus, and a chip manufacturing apparatus. The display manufacturingapparatus manufactures a color filter used in a liquid crystal displayand the like. The electrode forming apparatus forms an electrode used inan organic Electro Luminescence (EL) display, a field emission display(FED), and the like. The chip manufacturing apparatus manufactures abiochip (biochemical element). Liquid type ink drops are ejected from arecording head for an image recording apparatus. A solution is ejectedfrom a coloring material ejecting head for the display manufacturingapparatus. The solution contains a red (R) coloring material, a green(G) coloring material, and a blue (B) coloring material. Liquid typeelectrode material drops are ejected from an electrode material ejectinghead for the electrode forming apparatus. A biological organic materialsolution is ejected from a biological organic material ejecting head forthe chip manufacturing apparatus.

The liquid ejecting head is configured to introduce a liquid into apressure chamber, and generate a pressure fluctuation in the liquid inthe pressure chamber, so that the liquid may be ejected from a nozzlelinked to the pressure chamber. A pressure generator causes the pressurefluctuation to occur in the liquid in the pressure chamber. Apiezoelectric element is appropriately used as the pressure generator.The piezoelectric element is configured, for example, in such a mannerthat a lower electrode film, a piezoelectric layer, and an upperelectrode film are respectively stacked and formed in order from a sidenear the pressure chamber using a film forming technology. The lowerelectrode film functions as an individual electrode provided in or foreach pressure chamber. The piezoelectric layer is formed of leadzirconate titanate (PZT) and the like. The upper electrode filmfunctions as or is formed as a common electrode which is common to aplurality of pressure chambers (for example JP-A-2009-172878). A portionof the piezoelectric film interposed between the upper electrode filmand the lower electrode film is set to be an activation portion (activeportion) that is deformed by applying a voltage to the electrode films.Such a piezoelectric element is formed on a vibrating plate whichsub-divides the pressure chamber on one side (for example, a sideopposite to a nozzle plate in which the nozzle is formed). The vibratingplate has flexibility and is deformed depending on or according to thedeformation of the piezoelectric element.

If a piezoelectric element formed with a film shape is too thin, thepiezoelectric element may be bended too much in a state where a drivingvoltage is not applied to an electrode film (an initial state). This mayhave an impact on the ability of effectively eject liquid from thepressure chamber. Thus, it is necessary to consider that such apiezoelectric element is suppressed from excessively bending, that aneutral axis of the piezoelectric element is held at an appropriateposition and that a vibrating plate may be thick. With such a structure,it is possible to make the piezoelectric element have rigidity in anactivation portion (active portion) and to suppress the piezoelectricelement from excessively bending in the initial state. However, if thevibrating plate is thick, a portion on which a piezoelectric layer isnot stacked in an area corresponding to a pressure chamber has anexcessive thickness. In this case, deformation of the vibrating plate isprevented at the portion corresponding to the pressure chamber on whichthe piezoelectric layer is not stacked. Accordingly, the pressurefluctuation may be insufficiently transferred to liquid in the pressurechamber.

SUMMARY

An advantage of some aspects of the invention is to provide a liquidejecting head and a liquid ejecting apparatus that are capable ofsuppressing a piezoelectric layer from excessively bending withoutdeformation of a vibrating plate being prevented. Embodiments of theinvention ensure that the vibrating plate is sufficiently deformed whengenerating a pressure fluctuation in a pressure chamber even when thevibrating plate is thick and the piezoelectric layer is thin.

According to an embodiment of the invention, a liquid ejecting headincludes a pressure chamber formation substrate in which a plurality ofspaces are formed in a first direction. The spaces that communicate witha nozzle may be pressure chambers. A vibrating plate may be formed onone side of the pressure chamber formation substrate and may seal theone side of the pressure chambers formed in the pressure chamberformation substrate. The liquid ejecting head also includes apiezoelectric element obtained by stacking a first electrode layer, apiezoelectric layer, and a second electrode layer in order from avibrating plate side on the vibrating plate. The vibrating plate blocksan opening of the space in the pressure chamber formation substrate tosub-divide the pressure chamber. The first electrode layer is providedindependently for each pressure chamber and the second electrode layeris provided continuously through or for the plurality of pressurechambers. The first electrode layer is formed to have a width in thefirst direction that is narrower than a width of the pressure chamber inthe first direction at an area corresponding to the pressure chamber.The vibrating plate at the area corresponding to the pressure chamberincludes an area P1, an area P2, and an area P3. On the area P1, thepiezoelectric layer that is formed to be an activation portion (activeportion) is stacked, and the first electrode layer is interposed betweenthe activation portion and the vibrating plate. On the area P2, thepiezoelectric layer that is formed to be an inactivation (or inactive)portion is stacked. The first electrode layer is not interposed betweenthe inactivation portion and the vibrating plate on the area P2. On thearea P3 of the vibrating plate, the piezoelectric layer is not stacked.When the thickness of the vibrating plate at the area P1 is set to t1,the thickness of the vibrating plate at the area P2 is set to t2, andthe thickness of the vibrating plate at the area P3 is set to t3. In oneexample, the following expression is satisfied.t1>t2≧t3  (1)

According to an example configuration, the vibrating plate at the areaP1 is thicker than the vibrating plate at the area P2, and thus it ispossible to improve rigidity of the piezoelectric layer at theactivation portion including the area P1. A thicker vibrating plate inthe area P1 can help prevent the piezoelectric layer from excessivelybending in one example in the initial state. The vibrating plate at thearea P3 is thinner than the vibrating plate at the area P2, and thus itis possible to suppress movement of the vibrating plate from beingprevented on the outside of the piezoelectric layer and to sufficientlytransfer pressure fluctuation occurring by deformation of thepiezoelectric element to the liquid in the pressure chamber. In otherwords, because the thickness in the area P3 is thinner than the area P2and thinner than the area P1, the vibration plate in the area P3 deformssufficiently to generate an appropriate pressure fluctuation in theliquid in the pressure chamber. As a result, the liquid ejecting headhas high reliability.

In one configuration, the vibrating plate be obtained or formed bystacking silicon oxide and zirconium oxide in order from a pressurechamber side. The thickness of the zirconium oxide may be caused to varyin order to satisfy the expression (1).

According to one configuration, it is possible to form a zirconium oxidelayer at the areas P1 and P2 on which the piezoelectric layer isstacked. It is possible to suppress lead contained in the piezoelectriclayer from being diffused to a lower layer side (silicon oxide side)when lead zirconate titanate (PZT) is fired to form the piezoelectriclayer, for example.

In one configuration, a difference between the thickness t1 of thevibrating plate at the area P1 and the thickness t2 of the vibratingplate at the area P2 and a difference between the thickness t2 of thevibrating plate at the area P2 and the thickness t3 of the vibratingplate at the area P3 may be, respectively, equal to or more than 10 nm.

According to one configuration, it is possible to further reliablyimprove the rigidity of the piezoelectric layer and to further reliablysuppress movement of the vibrating plate on the outside of thepiezoelectric layer from being prevented. Embodiments of the inventionreliably ensure movement of the vibrating plate on the areas outside ofthe piezoelectric layer at least when generating a pressure fluctuationin the liquid being ejected.

A liquid ejecting apparatus according to one or more embodiments of theinvention includes the liquid ejecting head having the above-describedconfiguration.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described with reference to theaccompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view illustrating a configuration of an exampleof a printer, which is an example of a liquid ejecting apparatus.

FIG. 2 is an exploded perspective view of an example of a recordinghead.

FIG. 3 is a plan view of the recording head.

FIG. 4 is a schematic cross-section view taken in a direction orthogonalto a nozzle row and illustrating an example configuration of a mainsection of the recording head.

FIG. 5 is a cross-sectional view taken along line V-V in FIG. 3.

FIG. 6 is an enlarged view of an area VI in FIG. 5.

FIGS. 7A to 7C are schematic diagrams illustrating a process of forminga vibrating plate.

FIGS. 8A and 8B are schematic diagrams illustrating an example processof forming the vibrating plate.

FIG. 9 is a plan view of a recording head according to one embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments for implementing the invention will bedescribed with reference to the accompanying drawings. In theembodiments which will be described below, various limitations may beapplied to a specific example to be appropriate for the invention.However, embodiments of the invention are not limited so long as notdeparting from the scope of the invention in the description which willbe made below. In the description which follows, a liquid ejectingapparatus according to embodiments of the invention may include an inkjet printer (hereinafter, a printer) as an example. An ink jet recordinghead (hereinafter, recording head) which is one type of a liquidejecting head may be mounted in the ink jet printer.

A configuration of a printer 1 will be described with reference toFIG. 1. The printer 1 is an apparatus which records an image or the likeon a surface of a recording medium (one type of impact target) 2 such asa recording paper by ejecting liquid type ink drops. The printer 1includes a recording head 3, a carriage 4, a carriage moving mechanism5, a transporting mechanism 6, and the like. The recording head 3 isattached to the carriage 4. The carriage moving mechanism 5 moves thecarriage 4 in a main scanning direction. The transporting mechanism 6transports the recording medium 2 in a sub-scanning direction, which istransverse to the main scanning direction. The ink is a type of liquidaccording to embodiments of the invention. The ink is stored in an inkcartridge 7, which is used as and is an example of a liquid supplysource. The ink cartridge 7 is installed in the recording head 3 and isdetachable. The ink cartridge is disposed on a main body side of theprinter. Accordingly, the configuration may be employed in which the inkis supplied from the ink cartridge to the recording head through an inksupply tube or other suitable path.

The carriage moving mechanism 5 includes a timing belt 8. The timingbelt 8 is driven by a pulse motor 9 such as a DC motor. Accordingly, ifthe pulse motor 9 operates, the carriage 4 is guided along a guide rod10 which is constructed in the printer 1 and the carriage 4 performsreciprocating movement in the main scanning direction (width directionof the recording medium 2).

FIG. 2 is an exploded perspective view illustrating a configuration ofthe recording head 3 according to one embodiment. FIG. 3 is a plan view(top view) of the recording head 3. FIG. 3 illustrates a state in whicha sealing plate 20 which will be described later is not bonded. That is,FIG. 3 is a plan view of a vibrating plate 21 obtained by stackinglayers which will be described later. FIG. 4 and FIG. 5 illustrate aconfiguration of a main section of the recording head 3. FIG. 4 is aschematic cross-section view taken in a direction orthogonal to a nozzlerow. FIG. 5 is a schematic cross-sectional view taken in a nozzle rowdirection (cross-section taken along line V-V in FIG. 3).

The recording head 3 in one embodiment is configured in such a mannerthat a pressure chamber formation substrate 15, a nozzle plate 16, anactuator unit 14, a sealing plate 20, and the like are stacked. Thepressure chamber formation substrate 15 is a plate member formed from asilicon single crystal substrate in one embodiment. A plurality ofspaces is provided in parallel with a partition wall 22 a interposedbetween the plurality of spaces in the pressure chamber formationsubstrate 15. Each space may be set to be a pressure chamber 22(corresponding to space according to embodiments of the invention andappropriately referred to as a pressure chamber space below). Thepressure chamber space is a vacant portion which is long in a directionorthogonal to a nozzle row direction. The pressure chamber space isprovided to have a one-to-one correspond to a nozzle 25 in the nozzleplate 16. That is, the pressure chamber space (or the pressure chamber22) is formed along the nozzle row direction (a first direction). Thepressure chamber spaces (or the pressure chambers 22) are formed to havea pitch between the pressure chamber spaces (or the pressure chambers22) that is the same as a formation pitch between the nozzles 25. In oneembodiment, an upper portion opening (opening on an opposite side to anozzle 25 side) of the pressure chamber space (pressure chamber 22) hasa trapezoid shape, as illustrated in FIG. 3. Regarding a dimension ofthe pressure chamber space, the height (that is, thickness of thepressure chamber formation substrate 15) is set to approximately 70 μmand the length (dimension in a direction orthogonal to the nozzle rowdirection or a direction in which the pressure chambers are arranged inparallel) of the pressure chamber space (specifically, upper portionopening) is set to approximately 360 μm. The width w1 (dimension in thenozzle row direction or the direction in which the pressure chambers arearranged in a row) of the pressure chamber space (specifically, upperportion opening) illustrated in FIG. 5 is set to approximately 70 μm.Multiple rows of pressure chambers may be formed in the pressure chamberformation substrate 15.

As illustrated in FIG. 2, a communicating portion 23 is formed at anarea in the pressure chamber formation substrate 15 in the direction inwhich the pressure chambers (or the rows of pressure chambers) arearranged in parallel. The area is positioned outside of the pressurechamber space on a side (opposite side to a side on which the pressurechamber space communicates with the nozzle 25) of a longitudinaldirection of the pressure chamber space. The communicating portion 23passes through the pressure chamber formation substrate 15. Thecommunicating portion 23 is a vacant portion commonly connected to therespective pressure chamber spaces. The communicating portion 23communicates with the pressure chamber space through the ink supply path24. Rather, the communicating portion 23 communicates with a pluralityof pressure chamber spaces through a plurality of ink supply paths 24.The communicating portion 23 communicates with a communicating openingportion 26 of the vibrating plate 21 which will be described later and aliquid accommodation vacant portion 33 of the sealing plate 20, and thusa reservoir (common liquid chamber) is configured. The reservoir is anink chamber common to the respective pressure chamber spaces (pressurechambers 22). The ink supply path 24 is formed to have a width narrowerthan the width of the pressure chamber space. The ink supply path 24 isa portion which acts as passage resistance to the ink flowing in thepressure chamber space from the communicating portion 23.

The nozzle plate 16 (nozzle formation substrate) is bonded to a bottomsurface (surface of a side opposite to a side of a surface on which thepressure chamber formation substrate 15 and the actuator unit 14 arebonded) of the pressure chamber formation substrate 15. The nozzle plate16 is bonded with an adhesive, a thermal bonding film, or the like. Inone embodiment, the nozzles 25 are arranged in parallel with a pitch(inter-center distance between the adjacent nozzles 25) in the nozzleplate 16. The pitch corresponds to a dot formation density (for example,300 dpi to 600 dpi). The nozzle 25 communicates to or with an endportion of the pressure chamber space on a side opposite to the inksupply path 24. The nozzle plate 16 is manufactured by using, forexample, a silicon single crystal substrate, stainless steel or thelike.

The actuator unit 14 includes the vibrating plate 21 and a piezoelectricelement 19. The vibrating plate 21 is formed from an elastic film 17 andan insulator film 18. The elastic film 17 is formed of silicon oxide(SiO_(x)) (for example, silicon dioxide (SiO₂)) which is formed on anupper surface of the pressure chamber formation substrate 15. Theinsulator film 18 is formed of zirconium oxide (ZrO_(x)) which is formedon the elastic film 17. A portion of the vibrating plate 21corresponding to the pressure chamber space functions as a displacementportion. The portion is a portion obtained by sub-dividing a portion ofthe pressure chamber 22 with the upper portion opening of the pressurechamber space blocked. The displacement portion performs displacement ina direction far from or away from the nozzle 25 or in a direction closeto or towards the nozzle 25, in accordance to bending deformation of thepiezoelectric element 19. The vibrating plate 21 at the areacorresponding to the pressure chamber 22 is divided into three areas P1,P2, and P3 based on a positional relationship among an upper electrodefilm 29, a piezoelectric layer 28, and a lower electrode film 27 whichwill be described later. The three areas P1, P2, and P3 are formed insuch a manner that the vibrating plate 21 has a different thickness ateach of the three areas P1, P2, and P3. The description regarding thiswill be made below in detail. As illustrated in FIG. 2, a communicatingopening portion 26 is provided in a portion of the vibrating plate 21corresponding to the communicating portion 23 of the pressure chamberformation substrate 15. The communicating opening portion 26communicates with the communicating portion 23.

The piezoelectric element 19 is formed at a portion of the vibratingplate 21 (insulator film 18) corresponding to the pressure chamberspace, that is, on an upper surface (surface of an opposite side to anozzle 25 side) of the displacement portion. In one embodiment, thepiezoelectric element 19 is configured in such a manner that a lowerelectrode film 27 (corresponding to a first electrode layer in oneembodiment), a piezoelectric layer 28, and an upper electrode film 29(corresponding to a second electrode layer in one embodiment) arestacked in order from a vibrating plate 21 side using a film formingtechnology. As illustrated in FIG. 5, the lower electrode film 27 isprovided independently for each pressure chamber 22. The upper electrodefilm 29 is provided continuously through or for the plurality ofpressure chambers 22. Accordingly, the lower electrode film 27 is set tobe an individual electrode for each pressure chamber 22 and the upperelectrode film 29 is set to be a common electrode which is common to therespective pressure chambers 22.

Specifically, as illustrated in FIG. 3 and FIG. 5, both end portions ofthe upper electrode film 29 in the nozzle row direction extend beyond anedge of the upper portion opening of the pressure chamber space to theoutside of the plurality of the pressure chamber spaces (pressurechamber 22) which are provided in a row. Both of the end portions of theupper electrode film 29 in a longitudinal direction (directionorthogonal to the nozzle row direction) of the pressure chamber 22(pressure chamber space) are extended to the outside of thecorresponding pressure chamber space (pressure chamber 22) beyond anedge of the upper portion opening of the pressure chamber space. Thelower electrode film 27 in the longitudinal direction of the pressurechamber 22 (pressure chamber space) has an end portion on one side(upper side in FIG. 3) and an end portion on another side (lower side inFIG. 3). The end portion on the one side is extended to a locationoverlapped with the ink supply path 24 beyond the edge of the upperportion opening of the pressure chamber 22 and the end portion on theother side is extended to a lead electrode portion 41.

As illustrated in FIG. 5, the width w3 of the lower electrode film 27 inthe nozzle row direction over the pressure chamber space (at an areacorresponding to the pressure chamber 22) is narrower than the width w1of the pressure chamber 22 (specifically, the upper portion opening ofthe pressure chamber space) in the nozzle row direction. The width w2 ofthe piezoelectric layer 28 in the nozzle row direction over the pressurechamber space is narrower than the width w1 of the pressure chamber 22in the nozzle row direction and the width w2 is wider than the width w3of the lower electrode film 27 in the nozzle row direction. That is,dimensions in the nozzle row direction become smaller in order of thewidth of the upper electrode film 29, the width w1 of the pressurechamber 22, the width w2 of the piezoelectric layer 28, and the width w3of the lower electrode film 27.

In one embodiment, as illustrated in FIG. 3, the piezoelectric layer 28is divided so as to correspond to each piezoelectric element 19 by anopening portion 28 b. The opening portion 28 b is obtained by partiallyremoving the piezoelectric layer 28 (e.g., PZT layer 28 a).Specifically, the piezoelectric layer 28 is formed in such a manner thatthe piezoelectric layer 28 is extended to the outside of the pressurechamber 22 beyond both of the end portions (specifically, edges of theupper portion opening on both sides of the pressure chamber space) ofthe pressure chamber 22 in the longitudinal direction and thepiezoelectric layer 28 covers the plurality of pressure chambers 22. Thepiezoelectric layer 28 is partially removed at an area corresponding toa portion between adjacent pressure chambers 22. A plurality of theopening portions 28 b at which the piezoelectric layer 28 is not stackedis formed. That is, the plurality of the opening portions 28 b is formedin the nozzle row direction with the same pitch as a formation pitchbetween the pressure chambers 22 (formation pitch between the nozzles25). The opening portions 28 b correspond to areas where thepiezoelectric layer 28 has been removed. In other words, thepiezoelectric element 19 corresponding to one pressure chamber 22 isformed between the opening portion 28 b and the opening portion 28 bwith the same pitch as the formation pitch between the pressure chambers22. In other words, one pressure chamber is formed between adjacentopening portions 28 b. The opening portion 28 b in one embodiment isformed to have an elongated hexagonal shape (or other shape) which islong in the longitudinal direction of the pressure chamber 22, in a planview. The piezoelectric layer 28 at an area outside of the openingportion 28 b is formed continuously through or over the plurality of thepressure chambers in the longitudinal direction of the pressure chamber22.

In this manner, the piezoelectric element 19 is formed by stacking thelower electrode film 27, the piezoelectric layer 28, and the upperelectrode film 29. Thus, the piezoelectric layer 28 is formed over thelower electrode film 27 and the upper electrode film 29 is formed overthe piezoelectric layer 28. Accordingly, the vibrating plate 21 at anarea corresponding to the pressure chamber 22 is divided into the threeareas by overlapping portions of the respective films 27, 28, and 29.Specifically, the vibrating plate 21 is divided into the three areasincluding the area P1, the area P2, and the area P3. At the area P1, thelower electrode film 27, the piezoelectric layer 28, and the upperelectrode film 29 are stacked. The area P2 is outside of the lowerelectrode film 27 and the piezoelectric layer 28 and the upper electrodefilm 29 are stacked at the area P2. The lower electrode film 27 is notstacked at the area P2. The area P3 is outside of both the lowerelectrode film 27 and the piezoelectric layer 28 and only the upperelectrode film 29 is stacked at the area P3 (see FIG. 6). In oneembodiment, the areas P1, P2, and P3 are formed on both sides in thenozzle row direction, respectively. More specifically, for a givenpressure chamber, the areas P1, P2 and P3 are formed over both sides ofthe pressure chamber space in the nozzle row direction. Since the areasP1, P2, and P3 are formed to have bilateral symmetry, the areas on oneside will be mainly described below.

The piezoelectric layer 28 is interposed between the lower electrodefilm 27 and the upper electrode film 29 over the vibrating plate 21 atthe area P1. Thus, the piezoelectric layer 28 stacked at the area P1 isset to be the activation portion (active portion or active region) atwhich piezoelectric distortion occurs by applying a voltage to bothelectrodes. The piezoelectric layer 28 is not interposed between thelower electrode film 27 and the upper electrode film 29 on the vibratingplate 21 at the area P2 at which the lower electrode film 27 is notformed. Rather, the piezoelectric layer 28 is interposed between thevibrating plate 21 (insulator film 18) and the upper electrode film 29in the area P2. Thus, the piezoelectric layer 28 stacked at the area P2is set to be an inactivation portion (inactive portion or inactiveregion) at which piezoelectric distortion does not occur even though avoltage is applied to both of the electrodes.

In one example, the width w2 of the piezoelectric layer 28 may be set tobe in a range of 30 to 60 μm on the pressure chamber space in the nozzlerow direction and, in one embodiment, the width w2 is set toapproximately 52 μm. In one example, the width w3 of the lower electrodefilm 27 may be set to be in a range of 15 to 60 μm and, in oneembodiment, the width w3 is set to approximately 40 μm. In one example,a distance w4 (see FIG. 6) from an outer end portion of the lowerelectrode film 27 on one side to an outer end portion of thepiezoelectric layer 28 on the one side may be set to be in a range of2.5 to 8.0 μm. The distance w4 may also mean the width w4 of the area P2on the one side in the nozzle row direction. In one embodiment, thedistance w4 is set to approximately 6 μm.

The upper electrode film 29 and the lower electrode film 27 may beformed of various metals, the alloys of the various metals, and thelike. The various metals may include, but are not limited to, iridium(Ir), platinum (Pt), titanium (Ti), tungsten (W), tantalum (Ta),molybdenum (Mo), and the like. The piezoelectric layer 28 may be formedof a ferroelectric piezoelectric material such as lead zirconatetitanate (PZT), relaxor ferroelectrics, and the like. The relaxorferroelectrics are obtained by adding metal such as niobium, nickel,magnesium, bismuth and yttrium to the ferroelectric piezoelectricmaterial. In one example, the thickness of the upper electrode film 29may be set to be in a range of 15 to 100 μm and, in one embodiment, thethickness of the upper electrode film 29 is set to approximately 70 μm.In one example, the thickness of the piezoelectric layer 28(specifically, the thickness of the piezoelectric layer 28 at the areaP1) may be set to be in a range of 0.7 to 5 μm and, in one embodiment,the thickness of the piezoelectric layer 28 is set to approximately 1μm. In one example, the thickness of the lower electrode film 27 may beset to be in a range of 50 to 300 μm and, in one embodiment, thethickness of the lower electrode film 27 is set to approximately 150 μm.

The lead electrode portion 41 is formed at a location which ispositioned on the piezoelectric layer 28 at an area outside of the edgeof the upper portion opening of the pressure chamber space in thelongitudinal direction of the pressure chamber space and is separatedfrom the upper electrode film 29 by a predetermined distance (positionedon the left side of FIG. 4). As illustrated in FIG. 4, a through hole 42is formed to reach the lower electrode film 27 from the upper surface ofthe piezoelectric layer 28 at a position at which the lead electrodeportion 41 is formed in the piezoelectric layer 28 in a state of passingthrough the piezoelectric layer 28. The lead electrode portion 41 ispatterned corresponding to the lower electrode film 27 which is anindividual electrode. The lead electrode portion 41 is electricallyconnected with the lower electrode film 27 through the through hole 42.The driving voltage (driving pulse) is selectively applied to thepiezoelectric elements 19 through the lead electrode portions 41.

As illustrated in FIG. 2, a sealing plate 20 is bonded to an uppersurface of the actuator unit 14 opposite to a bottom surface. The bottomsurface is a bonding surface of the actuator unit 14 and the pressurechamber formation substrate 15. The sealing plate 20 includes anaccommodation vacant portion 32 able to accommodate the piezoelectricelement 19. A liquid accommodation vacant portion 33 is provided at anarea which is positioned outside of the accommodation vacant portion 32in a direction orthogonal to a nozzle row direction and corresponds tothe communicating opening portion 26 of the vibrating plate 21 and thecommunicating portion 23 of the pressure chamber formation substrate 15,in the sealing plate 20. The liquid accommodation vacant portion 33passes through the sealing plate 20 in the thickness direction of thesealing plate 20 and the liquid accommodation vacant portion 33 isprovided in a direction where the liquid accommodation vacant portion 33and the pressure chamber space (pressure chamber 22) are disposed inparallel. The liquid accommodation vacant portion 33 communicates withthe communicating opening portion 26 and the communicating portion 23 inseries to constitute a reservoir which is the ink chamber common to therespective pressure chamber spaces, as described above. A wiring openingportion (not illustrated) may be provided in the sealing plate 20 inaddition to the accommodation vacant portion 32 and the liquidaccommodation vacant portion 33. The wiring opening portion passesthrough the sealing plate 20 in the thickness direction of the sealingplate 20. An end portion of the lead electrode portion 41 is exposed inthe wiring opening portion. A terminal of a wiring member (notillustrated) from a main body side of a printer is electricallyconnected to an exposure portion of the lead electrode portion 41.

In the recording head 3 of the above-described configuration, the ink istaken from the ink cartridge 7 and a flow passage of the reservoir, theink supply path 24, the pressure chamber 22, and the nozzle 25 is filledwith ink. A driving signal is applied from the main body side of theprinter, and thus an electric field is given in accordance to apotential difference of both of the electrodes between the lowerelectrode film 27 and the upper electrode film 29 which correspond tothe pressure chamber 22. The displacement portion of the piezoelectricelement 19 and the vibrating plate 21 performs displacement inaccordance with the electric field or the applied voltage, and thuspressure fluctuation occurs in the pressure chamber 22. Control of thepressure fluctuation causes the ink to be ejected from the nozzle 25.

The recording head 3 according to one embodiment of the invention isconfigured in such a manner that a relationship of the thicknesses ofthe vibrating plate 21 at the area P1, P2, and P3 satisfies anexpression of P1>P2≧P3 such that the piezoelectric element 19(piezoelectric layer 28) is suppressed from excessively bending withoutdeformation of a vibrating plate 21 being prevented in a state where adriving voltage is not applied to both of the electrodes (initialstate), as illustrated in FIG. 6. That is, the recording head 3 isconfigured in such a manner that when the thickness of the vibratingplate at the area P1 is set to t1, the thickness of the vibrating plateat the area P2 is set to t2, and the thickness of the vibrating plate atthe area P3 is set to t3, the following (1) expression is satisfied.t1>t2≧t3  (1)

This configuration of the vibrating plate 21 ensures that, when in theinitial state, the piezoelectric element is not excessively bent. Anexcessively bend piezoelectric element may not be able to generate asufficient pressure fluctuation.

In one embodiment, the configuration is made in such a manner that theelastic film 17 is formed of silicon dioxide (SiO₂) and the thicknessesof the elastic film 17 at the area P1, P2, and P3 are matched to beconstant. The insulator film 18 is formed of zirconium oxide (ZrO_(x)and the thicknesses of the insulator film 18 at the area P1, P2, and P3are different from each other. Thus the above-described (1) expressionis satisfied. In one example, a difference between the thickness of thevibrating plate 21 (insulator film 18) at the area P1 and the thicknessof the vibrating plate 21 (insulator film 18) at the area P2 and adifference between the thickness of the vibrating plate 21 (insulatorfilm 18) at the area P2 and the thickness of the vibrating plate 21(insulator film 18) at the area P3 may be respectively in a range of 5to 50 nm. The differences may be equal to or more than 10 nm. Forexample, the thickness of the elastic film 17 may be set toapproximately 1500 nm. The thickness of the insulator film 18 at thearea P1 may be set to approximately 420 nm. The thickness of theinsulator film 18 at the area P2 may be set to approximately 380 nm. Thethickness of the insulator film 18 at the area P3 may be set toapproximately 340 nm. It is desired that the thickness of the elasticfilm 17 be set to be in a range of 300 to 2000 nm. In one example, thethickness of the insulator film 18 at the area P1 may be equal to orless than 600 nm. In one example, the thickness of the insulator film 18at the area P3 may be equal to or more than 30 nm.

In this manner, the vibrating plate 21 is thick at the area P1 at whichthe lower electrode film 27, the piezoelectric layer 28, and the upperelectrode film 29 are stacked, and thus it is possible to improverigidity of the piezoelectric layer 28 which is set to be or which islocated in the activation portion. That is, it is possible to make thepiezoelectric element 19 at the area P1 have rigidity to the extent ofappropriate descent of the neutral axis and to suppress thepiezoelectric element from excessively bending in the initial state. Thevibrating plate 21 is thin at the area P3 which is outside of the lowerelectrode film 27 and the piezoelectric layer 28 and at which only theupper electrode film 29 is stacked, and thus it is possible to suppressmovement of the vibrating plate 21 from being prevented on the outsideof the piezoelectric layer 28 and to sufficiently transfer pressurefluctuation occurring by deformation of the piezoelectric element 19 tothe ink in the pressure chamber 22. That is, it is possible to reducetransfer loss in transferring a driving force in the piezoelectricelement 19 to the ink in the pressure chamber 22. The relative thinnessof at the area P3 ensures that the vibration plate 21 deforms while therelative thickness at the area P1 ensures that the piezoelectric layeris not excessively bended in an initial state.

Accordingly, it is possible to suppress the driving voltage of thepiezoelectric element 19 required for ejecting a predetermined amount ofthe ink from the nozzle 25 from decreasing. It is possible to achievepower savings and to extend the life span of the piezoelectric element19. As a result, the reliability of the recording head 3 is improved.Furthermore, the insulator film 18 formed of zirconium oxide (ZrO_(x) isformed at the areas P1 and P2 at which the piezoelectric layer 28 isstacked, and thus it is possible to suppress lead contained in thepiezoelectric layer 28 from being diffused to a lower layer (elasticfilm 17) side when lead zirconate titanate (PZT) is fired to form thepiezoelectric layer 28. A difference between the thickness of thevibrating plate 21 at the area P1 and the thickness of the vibratingplate 21 at the area P2 and a difference between the thickness of thevibrating plate 21 at the area P2 and the thickness of the vibratingplate 21 at the area P3 may be respectively equal to or more than 10 nm.Thus it is possible to further reliably improve rigidity of thepiezoelectric layer 28 and to further reliably suppress movement of thevibrating plate 21 from being prevented on the outside of thepiezoelectric layer 28. In other words, it is possible to ensureadequate flexibility of the vibrating plate 21 on the outside of thepiezoelectric layer 21

The configuration may be made in such a manner that the thickness of thevibrating plate 21 at the area P2 is equal to the thickness of thevibrating plate 21 at the area P3 and the upper surface of the insulatorfilm 18 is formed to be flat in the boundary between the area P2 and thearea P3. That is, “t2=t3” may be set. In this case, the vibrating plate21 at the area P1 may be also thick, compared to the vibrating plate 21at the area P2 and the area P3, and thus it is possible to improverigidity of the piezoelectric element 19 at the area P1. Meanwhile,since the vibrating plate 21 at the areas P2 and P3 is thin, it ispossible to suppress movement of the vibrating plate 21 on the outsideof the piezoelectric layer 28 from being prevented and to sufficientlytransfer pressure fluctuation occurring by deformation of thepiezoelectric element 19 to the ink in the pressure chamber 22. If thevibrating plate 21 at the area P3 is thinner than the vibrating plate 21at the area P2, that is, if “t2>t3” is set, it is possible to furthersuppress movement of the vibrating plate 21 from being prevented.

A manufacturing method of the vibrating plate 21 and the piezoelectricelement 19 will be described below. First, the insulator film 18, whichis formed of zirconium oxide (ZrO_(x,)) is formed on the elastic film17, which is formed of silicon dioxide (SiO₂), using a sputtering methodor the like. Then, as illustrated in FIG. 7A, a lower metal layer 27 ato be the lower electrode film 27 is formed on the entire surface of theinsulator film 18 using a sputtering method or the like. Thereafter, thelower metal layer 27 a is patterned to have a predetermined shape byetching. Specifically, a pattern to be a mask for etching is provided onthe lower metal layer 27 a using a photolithography method or the like.The lower metal layer 27 a is etched from an upper surface of the lowermetal layer 27 a using an etching solution which is an aqueous solutionor the like. At this time, etching is performed equal to or more thanthe thickness of the lower metal layer 27 a by controlling an etchingtime and the like. Thus, as illustrated in FIG. 7B, the insulator film18 corresponding to an area (areas P2 and P3) other than the lower metallayer 27 a remaining as the lower electrode film 27 is etched. In thisexample, the insulator film 18 corresponding to the vibrating plate 21at the area P1 is not etched, the lower electrode film 27 is formed onthis insulator film 18, and the insulator film 18 corresponding to thevibrating plate 21 at the area P2 and the area P3 is over-etched. As aresult, a level difference at the boundary between the area P1 and thearea P2 is formed and the insulator film 18 corresponding to the areasP2 and P3 is lower than a portion corresponding to the area P1 by onestep.

If the lower electrode film 27 is formed on the insulator film 18, asillustrated in FIG. 7C, the PZT layer 28 a to be a piezoelectric layer28 is formed on the entire surface of the insulator film 18 on which thelower electrode film 27 is formed. A forming method of the PZT layer 28a is not particularly limited. For example, a sol-gel method is used inwhich a so-called sol which is dissolved and distributed using a metalorganic material as a catalyst is applied and dried to be a gel and thegel is fired at a high temperature to obtain the PZT layer 28 a formedof a metallic oxide. Additionally, the PZT layer 28 a may be formedusing various methods of a sputtering method, an IJ applying method, andthe like. Thereafter, a pattern to be a mask for etching is formed onthe PZT layer 28 a by using a photolithography method and the PZT layer28 a is patterned by etching to have a predetermined shape. At thistime, etching is performed equal to or more than the thickness of thePZT layer 28 a by controlling an etching time and the like. Asillustrated in FIG. 8A, the insulator film 18 corresponding to an area(area P3) other than the PZT layer 28 a remaining as the piezoelectriclayer 28 including the opening portion 28 b is etched. In this example,the insulator film 18 corresponding to the vibrating plate 21 at theareas P1 and P2 is not etched, the piezoelectric layer 28 is formed onan upper surface of the insulator film 18, and the insulator film 18corresponding to the vibrating plate 21 (opening portion 28 b) at thearea P3 is over-etched. As a result, a level difference at the boundarybetween the area P2 and the area P3 is formed and the insulator film 18corresponding to the area P3 is lower than or thinner than the insulatorfilm 18 corresponding to the area P2 by one step. The area P2 and thearea P3 may have the same thickness without etching (over-etching) thePZT layer 28 a equal to or more than the thickness of the PZT layer 28a.

Then, as illustrated in FIG. 8B, an upper metal layer 29 a to be theupper electrode film 29 is formed on the entire surface of the insulatorfilm 18 on which the lower electrode film 27 and the piezoelectric layer28 are formed, by using a sputtering method or the like. A pattern to bea mask for etching is formed on the upper metal layer 29 a by using aphotolithography method and the upper metal layer 29 a is patterned tohave a predetermined shape by etching. In this manner, the vibratingplate 21 and the piezoelectric element 19 according to one embodimentmay be formed.

Embodiments of the invention are not limited to the above-describedembodiments and various modifications may be made based on thedescription herein.

For example, in one embodiment, the vibrating plate 21 at the area P3 isconfigured by the two layers of the elastic film 17 and the insulatorfilm 18, but is not limited thereto. For example, the insulator film maybe completely removed and the vibrating plate at the area P3 may beconfigured by only the elastic film. That is, the insulator film at thearea P3 may have a thickness of 0 nm. The main point is that theinsulator film at the area P3 may have a thickness of any value as longas the insulator film (vibrating plate) at the area P3 is thinner thanthe insulator film (vibrating plate) at the area P2 or equal inthickness to the area P2. The shape of the pressure chamber 22 (pressurechamber space) is not limited to the above-described embodiments. Forexample, an inner wall surface sub-dividing the pressure chamber spacemay be inclined to the top surface and the bottom surface of thepressure chamber formation substrate. In this case, the width of thepressure chamber corresponds to the opening width of the upper portionopening of the pressure chamber space. Thus, the width of the pressurechamber may vary with respect to the thickness direction of the pressurechamber formation substrate.

In the above-described embodiments, among the areas of the vibratingplate 21 corresponding to the pressure chamber 22, the entirety of anarea at which the lower electrode film 27, the piezoelectric layer 28,and the upper electrode film 29 are stacked is set to be the area P1,the entirety of an area which is outside of lower electrode film 27 andat which the piezoelectric layer 28 and the upper electrode film 29 arestacked is set to be the area P2, and the entirety of an area which isoutside of the lower electrode film 27 and the piezoelectric layer 28and at which only the upper electrode film 29 is stacked is set to bethe area P3. However, the respective areas P1, P2, and P3 are notlimited thereto. Each area may include an area at which the thickness ofthe vibrating plate is different from each other. For example, an areawhich is outside of the lower electrode film 27 and at which thepiezoelectric layer 28 and the upper electrode film 29 are stacked mayinclude an area P2 with the thickness of t2 and an area P2′ with thethickness larger than or smaller than t2. An area which is outside ofthe lower electrode film 27 and the piezoelectric layer 28 and at whichonly the upper electrode film 29 is stacked may include an area P3 withthe thickness of t3 and an area P3′ with the thickness larger than orsmaller than t3. This may be applied to the area P1, similarly.Particularly, when the area P2′ is thicker than the area P2, if the areaP2 is wider than the area P2′, the effect that the deformation of thevibrating plate is not prevented is largely improved. This may beapplied to a case where the area P3′ is thicker than the area P3,similarly. Such a difference between the thicknesses of the vibratingplate at the respective areas may be formed due to manufacturingtolerance.

In the above-described embodiments, the upper portion opening of thepressure chamber space (pressure chamber 22) has a trapezoid shape andthe opening portion 28 b formed in the piezoelectric layer 28 has anelongated hexagonal shape, but the shapes of the upper portion openingof the pressure chamber space and the opening portion 28 b formed in thepiezoelectric layer 28 are not limited thereto. The pressure chamberspace (pressure chamber), the piezoelectric layer (opening portion), therespective electrode films, and the like may have various shapes.

For example, in a recording head 3′ according to an embodimentillustrated in FIG. 9, an upper portion opening of a pressure chamberspace (pressure chamber 22′) has a substantially elliptical shape in aplan view. A lower electrode film 27′ is formed with a substantiallyelliptical shape such that the shape of the lower electrode film 27′matches the shape of the pressure chamber 22′. An opening portion 28 b′of the piezoelectric layer 28′ is formed on both sides of the pressurechamber 22′ in the nozzle row direction, along an edge of an upperportion opening of the pressure chamber 22′. An upper electrode film 29′is extended to the outside of a plurality of pressure chambers 22′ whichare provided in series in a direction in which the pressure chambers 22′are arranged in series (nozzle row direction), similarly to the upperelectrode film 29 in the above-described embodiments. The upperelectrode film 29′ in a longitudinal direction of the pressure chamber22′ has an end portion on one side (upper side in FIG. 9) and an endportion on another side (lower side in FIG. 9). The end portion on oneside is extended to a location overlapped with an ink supply path 24′.The end portion on the other side is extended to the outside of thepressure chamber 22′.

In one embodiment, dimensions of the respective layers in the nozzle rowdirection become smaller in order of the width of the upper electrodefilm 29′, the width of the pressure chamber 22′, the width of thepiezoelectric layer 28′, and the width of the lower electrode film 27′.Accordingly, there are three areas; an area P1 at which the lowerelectrode film 27′, the piezoelectric layer 28′, and the upper electrodefilm 29′ are stacked, an area P2 which is outside of the lower electrodefilm 27′ and at which the piezoelectric layer 28′ and the upperelectrode film 29′ are stacked, and an area P3 which is outside of thelower electrode film 27′ and the piezoelectric layer 28′ and at whichonly the upper electrode film 29′ is stacked. The thicknesses t1 to t3of the vibrating plate at the respective areas P1 to P3 are configuredin such a manner that the expression (1) is satisfied. With theseexample configurations, it is possible to suppress the piezoelectriclayer 28′ from excessively bending in the initial state and to suppressmovement of the vibrating plate on the outside of the piezoelectriclayer 28′ from being prevented. In other words, the thickness of thearea P1 can help prevent the piezoelectric layer 28′ from excessivelybending while the thinner thickness of the area P2 and/or P3 ensure thatthe vibration plate can be sufficiently deformed such that liquid can beappropriately ejected from the pressure chamber. Other components arethe same as the components in the above-described embodiment and thedescriptions thereof will be omitted.

In the above-described embodiments, an ink jet type recording headmounted in an ink jet printer is described as an example. However, if adevice includes the piezoelectric element and the pressure chamber inthe configuration, the device may be applied to an apparatus ejectingliquid other than the ink. The embodiments according to the inventionmay be applied to a coloring material ejecting head, an electrodematerial ejecting head, a biological organic material ejecting head, andthe like, for example. The coloring material ejecting head is used inmanufacturing of a color filter of a liquid crystal display or the like.The electrode material ejecting head is used in forming of an electrodeof an organic Electro Luminescence (EL) display, a field emissiondisplay (FED), and the like. The biological organic material ejectinghead is used in manufacturing of a biochip (biochemical element).Additionally, embodiments are not limited to an apparatus including apiezoelectric element which is functionally deformed by applying avoltage and functions as a so-called actuator and the embodiments may beapplied to an apparatus including a piezoelectric element whichpassively outputs an electric signal by receiving movement from theoutside of the piezoelectric element and functions as a so-calledsensor.

What is claimed is:
 1. A piezoelectric device comprising: a pressurechamber formation substrate in which a plurality of spaces is formed ina first direction; and a piezoelectric element that includes a firstelectrode layer, a piezoelectric layer, and a second electrode layerthat are stacked in order on a vibrating plate that covers the pressurechamber formation substrate so as to block the plurality of spaces,wherein: the first electrode layer is provided independently for eachpressure chamber and the second electrode layer is provided continuouslyfor the plurality of the pressure chambers, the first electrode layer isformed to have a width in the first direction that is narrower than awidth of the pressure chamber in the first direction at an areacorresponding to the pressure chamber, the vibrating plate, at the areacorresponding to the pressure chamber, includes an area P1, an area P2,and an area P3, the area P1 corresponds to an area on which anactivation portion of the piezoelectric layer is stacked, the area P2corresponds to an area on which an inactivation portion of thepiezoelectric layer is stacked, and the area P3 corresponds to an areaon which the piezoelectric layer is not stacked, and when a thickness ofthe vibrating plate at the area P1 is set to t1, a thickness of thevibrating plate at the area P2 is set to t2, and a thickness of thevibrating plate at the area P3 is set to t3, the following expression issatisfied,t1>t2≧t3.
 2. The piezoelectric device according to claim 1, wherein thevibrating plate includes silicon oxide and zirconium oxide stacked inorder from a pressure chamber side, and the thickness of the zirconiumoxide is caused to vary in order to satisfy the expression t1>t2≧t3. 3.The piezoelectric device according to claim 1, wherein a differencebetween the thickness t1 of the vibrating plate at the area P1 and thethickness t2 of the vibrating plate at the area P2 and a differencebetween the thickness t2 of the vibrating plate at the area P2 and thethickness t3 of the vibrating plate at the area P3 are respectivelyequal to or more than 10 nm.
 4. A piezoelectric device comprising: apressure chamber formation substrate that includes a plurality ofpressure chambers; a vibration plate formed on the pressure chamberformation substrate; a plurality of piezoelectric elements, wherein eachpressure chamber is associated with one of the plurality ofpiezoelectric elements, each piezoelectric element including a firstelectrode layer, a piezoelectric layer, and a second electrode layer;wherein the first electrode layer is provided independently for eachpressure chamber and the second electrode layer is common for theplurality of the pressure chambers, wherein the vibration plate includesa first area having a first thickness and a second area having a secondthickness and a third area having a third thickness, wherein the firstelectrode layer, the piezoelectric layer, and the second electrode layerare stacked at the first area, wherein the piezoelectric layer and thesecond electrode layer are stacked at the second area and wherein thefirst electrode layer is not stacked at the second area, wherein thesecond electrode layer is stacked at the third area and wherein thepiezoelectric layer and the first electrode layer are not stacked at thethird area, and wherein the second thickness is less than the firstthickness and the third thickness is less than the second thickness.